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In this MIDI-audio Patch circuit the capacitor has several lines though it - the lines look like ground lines - what do they represent ?

Does one connect the up and down triangles to each other, or are they separate (i.e. keep up triangles separate from down triangles ). I am assuming they are signal ground Thank you

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marked as duplicate by CL., ThreePhaseEel, Dmitry Grigoryev, Voltage Spike, Daniel Grillo Jan 16 '17 at 20:00

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  • \$\begingroup\$ The triangles should be connected together.yheyvare the same net irrespective of inclination. The "several lines" are also ground. The purpose of that is a good question. The polarity marking mat hive away the idea I am not sure \$\endgroup\$ – Umar Jan 15 '17 at 6:54

The triangles "connected" to one of the terminals of each capacitors is a notation to let you know that that wire jumps to somewhere else on the schematic. If they're not labeled they're usually considered obvious for the intended audience of the schematic drawer. That's not to say this isn't ambiguous. I would have labeled them here.

Capacitors with lines drawn between the plates like that indicate that it is an electrolytic capacitor. The + signs also point to that. Other capacitors don't have polarity. I'd guess the lines could be best said to represent the electrolyte goo that's inside an electrolytic capacitors. I'd recommend the wikipedia article on capacitors if you want some in depth info on how they work.

I'm 99.9% sure those capacitors are power supply capacitors meant to smooth any ripples and shunt any noise to ground. I have a few reasons for this:

  1. Those capacitors are both connected to ground but with opposite polarities. Audio circuits and many others use two power supply rails of the same voltage magnitude but opposite signs with respect to ground. This makes it easier to have your signals have an average voltage of 0V(aka no dc component). Typically a single rail circuit would need DC blocking capacitors and these are undesirable for many reasons. One big one is that capacitors have a frequency dependent impedance. They are useful as filters for this reason.

  2. They're electrolytic and electrolytic capacitors are ideally suited for this purpose due the sign of the voltage never changing and electrolytic offer more capacitance per weight, price, size than other capacitors. Their major drawback is they don't work and might even be destroyed if a reverse voltage is applied to them. There are other places where they can be used but with the other points I have I am very sure.

  3. They're identically rated and right next to each other. Those capacitors could have been placed anywhere on the schematic there was free space because of how isolated they are. Being together is a possible clue especially with the other points.

I am even more sure those triangles aren't connecting to each other. That would mean they share two connections. Since their polarities are reversed that would mean no voltage could be applied without unpredictable effects because one of the capacitors would have a reverse voltage on them.

My best guess is you have a +/- 12V power supply somewhere. Next guess would be 9V then 5V. If you have a drawing of the PCB or an actual model you could look for some printing that says C1 and C2 and follow the traces.

  • \$\begingroup\$ it might be a +/- 15v supply, but shouldn't be ;-) +1 for obvious but ambiguous! \$\endgroup\$ – Neil_UK Jan 15 '17 at 7:56

I have seen this answered more than once on stack exchange. It is the symbol for an electrolytic capacitor used in Japanese schematics.


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